This invention relates to a method of molding cloth, and more particularly, to a method of molding a multi-layer, vacuum-formable cloth which may be employed as the outer covering of seat cushions, acoustical dividers and the like.
The traditional method of making upholstered seat cushions involves: (1) cutting the cover material according to an appropriate pattern; (2) sewing the cut material; and (3) stuffing the cushion. High labor costs result, since, in many situations, the cutting and sewing operations are extensive and much must be performed by hand.
To reduce the cost of manufacturing seat cushions, a molding process was devised for manufacturing seat cushions comprising a foam portion having an integral vinyl cover. The vinyl covering is first heated and then drawn into a cold mold by means of a vacuum between the vinyl and the mold. As the vinyl cools, it assumes the contours of the mold. Foam is then poured into the mold to form the integral foam portion of the seat cushion. This process significantly reduces manufacturing costs and results in a superior seat.
However, cloth has many advantages over vinyl. Specifically, cloth is water vapor permeable. Perspiration that normally collects behind a person sitting in a vinyl seat can pass through cloth and be evaporated so that cloth feels cooler during warm weather and warmer during cold weather. Furthermore, the feel of the cloth, the "hand", is much more luxurious and elegant.
To reduce the expense of cloth covered seats, attempts have been made to develop cloth molding processes similar to that described above with respect to vinyl. U.S. Pat. No. 3,954,537 to Alfter et al discloses a process for producing multi-layer sheets having a polyurethane foam layer bonded to a cross-linked polyethylene foam layer. After discloses that it is particularly advantageous to join the foam layers with further layers such as fabric to form upholstery components. Alfter relies on the strength of the bond between the polyurethane foam and polyethylene foam to accomplish the molding. However, polyurethane foam in an uncured state can easily change shape. Since Alfter relies on the bonding of two foam layers, and not on the setting in some manner of the outer fabric layer, intricate detail is most likely not possible, and since polyurethane foam in an uncured state can change shape easily, it appears likely that the fabric layer would tend to return to its flat shape.
German Offenlegungsschrift No. 2,227,143 to Bayer AG, discloses a seat cushion with a textile cover and foam core. A fabric is bonded to a polyether-urethane foam layer which in turn is bonded to a film sealing layer. This multi-layer fabric is first heated to 70.degree. C. (158.degree. F.) and then drawn into a mold. A soft foam is then poured into the mold to form a seat cushion.
The following patents describe methods of forming a multi-layer cloth similar to that described above:
U.S. Pat. No. 3,941,633-Wang et al (1976)
U.S. Pat. No. 3,933,548-Anderson et al (1976)
U.S. Pat. No. 3,748,217-May et al (1973)
British Pat. No. 1,227,760-Dunlop (1971).
Although the cloth molding processes described in Bayer and Alfter do work with some molds and fabrics, the applications are rather limited. For example, the Bayer Patent recites that only elastic knit fabrics may be employed. The complexity of the mold pattern is also significantly limited. In the Bayer and Alfter processes, the molded fabric will not retain the contours of more intricate or sharp mold features.
One of the problems with the prior art procedures is that the stitch of the fabric layer is not set in the shape of the mold. Therefore, the fabric layer tends to pull against the other cloth layers or the underlying foam core. Over time details of the mold will tend to flatten.